Physical / Chemical Drivers

of the Ocean

in a High CO2 World

Laurent Bopp

IPSL / LSCE, Gif s/ Yvette, France

Sediment

Marine Biogeochemistry

Atmospheric Components :

CO2, DMS, CH4, N2O,…

Circulation, Temperature, Light, Dust, …

Ocean

Atmosphere

Biosphere Soils

Climate

IntroductionFood Web / Fisheries

Introduction

1850 1900 1950 2000 20502100

Tem

pera

ture

Change

(°C

)Pre

cipit

ati

on C

hang

e (

%)

Max.

Atl

anti

c O

ver.

(%

)

0

2

4

6

0

3

6

9

-15

-5

5

Coupled Model’sresponse to increasedAtmospheric pCO2

(IS92a, IPCC 2001)

Which aspects arerelevant to marinebiogeochemistry ?

Introduction

Drivers of Marine Biogeochemistry

Atmospheric pCO2

Temperature

Circulation(Advection & Mixing)

Light Supply

Dust Deposition

Rivers Input …

Marine Biogeochemistry

Carbon Cycle

O2 Cycle

Nutrients Cycle

Marine Productivity

Ecosystem Structure

Tools : Ocean-Atmosphere General Circulation Models

IPSL Coupled Model

PO43-

Particles

Euphotic Layer (100-150m)

PO43- Phyto

Zoo

Particles

Dissolved

PO43-

Diatoms

MicroZoo

P.O.M

D.O.M

Si

IronNano-phyto

Meso Zoo

NO3-

NH4+

Small Ones Big Ones

Tools : Biogeochemical Models for the Global Ocean

Geochemical Models …… to ….. Simple Ecosystem Models

Outline

Atmospheric pCO2

Temperature

Circulation(Advection & Mixing)

Light Supply

Dust Deposition

Rivers Input …

Carbon Cycle

O2 Cycle

Nutrients Cycle

Marine Productivity

Ecosystem Structure

1. Increased Atmospheric pCO2

Outline

Atmospheric pCO2

Temperature

Circulation(Advection & Mixing)

Light Supply

Dust Deposition

Rivers Input …

Carbon Cycle

O2 Cycle

Nutrients Cycle

Marine Productivity

Ecosystem Structure

1. Increased Atmospheric pCO2

2. Oceanic Circulation (Advection / Mixing)

Outline

Atmospheric pCO2

Temperature

Circulation(Advection & Mixing)

Light Supply

Dust Deposition

Rivers Input …

Carbon Cycle

O2 Cycle

Nutrients Cycle

Marine Productivity

Ecosystem Structure

1. Increased Atmospheric pCO2

2. Oceanic Circulation (Advection / Mixing)

3. Atmospheric Dust Deposition

Changes in pH : Acidification

Increase in DIC leads to an acidification of Ocean waters

Changes in Surface pH

IS92a, IPSL model, 2099-PreIndus

+0.5

+0.3

-0.3

-0.5

(See Poster by J. Orr)

All OCMIP2 Models

0-0.2-0.4

0°

40°N

40°S

Changes in pH & Marine Production / Ecosystem

Many studies have revealed/estimated the impact on marine ecosystems

Changes in CaCO3 Production (%), 2200 - PreIndustrial

Impact of Acidification on Marine CaCO3 Production (C. Heinze, HAMOCC4)

Changes in Ocean Physics : Stratification

-1000

+1000

+100

+10

0

-10

-100

IPSL-CM2, MML, 2075-Present

Shoaling of Max. Mixed Layer Depth…

(m)

(m)

Shoaling

80°S

40°S

0°

40°N

80°N

Sarmiento et al. in press

Consistent in 6 OAGCMs

IPSLNCARPrincetonMPIMHadleyCSIRO

Changes in Ocean Physics : Stratification

+1000

+100

+10

0

-10

-100

(m)

80°S

40°S

0°

40°N

80°N

Sarmiento et al. in pressMechanisms of Changes

(psu)(°C)

Mixed LayerSSSSST

80°S

40°S

0°

40°N

80°N

Changes in Winds : increase in Southern Ocean but …

Changes in Ocean Physics : Stratification

Implications for the Carbon Cycle

Implications for the Oxygen Cycle

Implications for Marine Productivity & Ecosystem

Changes in Ocean Physics & Carbon Cycle

IPCC, 2001

Climate Change reduces ocean CO2 sink(from –6% to –25% in 2050)

Climate ChangeImpact

Changes in Ocean Physics & Carbon Cycle

Mechanisms

Thermal Circulation

Re-Organisation of the Natural C Cycle

Sarmiento 96

Matear 99

Joos 99

(in GtC/yr, 1850-2100)

-52 -117 +111

-48 -41 +33

-68 -15 +33

Climatic Effect on CO2 sink at 4xCO2

gC m-2 yr-1

Decrease sink

Increase sink

Stratification prevents anthropogenic CO2 penetration

(HAMOCC3-OPA-LMD)

Changes in Ocean Physics & Carbon Cycle

Main Effect :

Changes in Ocean Physics & Oxygen Cycle

Recent data have shown O2 decreases in most regions of the ocean in the past 40 years (Emerson et al. 2001, Ono et al. 2001, Wanatabe et al. 2001, Matear et al. 2000, …)

Models suggest an amplification of this decrease in the coming decades(Bopp et al. 2002, Plattner et al. 2002, Matear et al. 2000,…)

Dep

th

Zonal Mean, Global Ocean, Changes in O2, 2100 - Present

The main driver is stratification (reduced ventilation & mixing)

Changes in Ocean Physics & Oxygen Cycle

Focus on the Equatorial Pacific

Dissolved O2 at 100 m(mol/l)

Anoxic / Suboxic Zone increases by 30 % in 2100

Changes in Ocean Physics & Oxygen Cycle

Mechanisms of Changes (3°S, Equatorial Pacific)

Temperature & Currents

Changes in T & U(2090-1990)

0 m

300 m

0 m

300 m

SEC

South Equatorial Current : shallower and weaker

No more warm & oxygenated water to the sub-surface

Changes in Ocean Physics & Marine Productivity

Mechanistic Models of Marine Biology

Empirical Models based on Observational constraints

(see Poster by P. Schultz)

Different approaches may be used…

• Similar response with different bio & dynamical models

Zonal Mean(2100-1990)

-30 % +30 %

• Decreases globally (-5/10%) BUT increases at high latitudes (+20/30%)

Simulation NPZD-IPSL, 2100-1990 30 gC m-2 an -1

- 30 gC m-2 an -1

Changes in Ocean Physics & Marine Productivity

Ocean Stratification increasesSurface nutrient -5 to –10 %

Oligotrophic GyresArea increases

Opposition high/low latitudes

(NPZD-IPSL)

Growing Season lenghtens

> +10 days

1xCO2 2xCO2-1xCO2

Changes in Ocean Physics & Marine Productivity

Changes in Ocean Physics & Marine Productivity

(m)

80°S

40°S

0°

40°N

80°N

Sarmiento et al. in press

80°S

40°S

0°

40°N

80°N

(days)

Less Nutrient … But Longer Growing Season IPSLNCARPrincetonMPIMHadleyCSIRO

Changes in Ocean Physics & Marine Ecosystem

Boyd and Doney (2002)

Increase in N2 fixationwith Global Warming

-1

+1

+0.02

-0.02

-0.2

+0.2

Bopp (2001)

Decrease in diatoms relative abundance

Changes in Dust Deposition

Recent papers suggest a high sensitivity of atmospheric dust loading to climate change

Mahowald and Luo (2003) : dust loading changes-20 / -60 %

Tegen et al. (2004) : dust loading changes +10 / -25 %

Mechanisms of changes

Sources of Dust Land Use CO2 Fertilization Climate Change

Transport

Changes in Dust Deposition & Marine Productivity Dust Deposition ……… and annual-mean Chlorophyll (M. Werner & I. Tegen) (PISCES model, O. Aumont)

(mg/m3)

5

0

1

(see talk by O. Aumont)

-0.5

+0.5

+0.1

-0.1

-0.5

+0.5

+0.1

-0.1

Sensitivity Exp: Dust deposition x2 or /2 (20 yr) Chl (mg/m3)

Conclusions

In a high CO2 world, the ocean will be…

More acidicMore stratifiedMore oligotrophic, but better light conditions Less oxygenated

But large uncertainties remain… in particular concerning …

Ocean Physics (Mixing ? Southern Ocean Circulation ?) Dust Deposition Changes Impact on Ecosystem Structure

Many Thanks to …

O. Aumont, J. Orr & OCMIP, C. Heinze, J. Sarmiento, I. Tegen, M. Werner, …

Oceanic Carbon Cycle : Oceanic Carbon Cycle : Coupling climate and carbon

1860 2000 2100

Coupled simulation

Observations

pCO2 (ppm)

Climate (OPA-LMD)

Carbon models(HAMOCC3,SLAVE)

pCO2

Emissions

Climatic effect : - pCO2 : + 70 ppm (20 %) - Temperature : ~15-20 %

Uncoupled simulation

Comparison to Cox et al. 2000

IPSL : 700 ppm 770 ppm

Geochemical Flux (gC m-2 an-1) of anthropic CO2

at 700 ppm Hadley

IPSL (OPA-LMD-HAMOCC3)

Differences :

- Terrestrial Biosphere

- Oceanic SinkSouthern Ocean

Hadley : 700 ppm 950 ppm

Climatic Effect

Ocean Carbon Cycle : Ocean Carbon Cycle : Coupling carbon and climateCoupling carbon and climate

Diatoms Abundance with Global Warming (using the PISCES model)

Diatoms replaced by NanoPhytoat mid/high Latitudes

Mechanisms :

Stratification

Nutrient Supply

Silica and Iron Limitation

Diatoms/ NanoPhyto

Changes in Diatoms Abundance (2090-1990)

-1

+1

+0.02

-0.02

-0.2

+0.2